The field of the present invention is golf club shafts and, more particularly, reduced weight golf club shafts and methods of manufacturing the same.
Recently, substantial attention has been directed toward the development of lightweight golf club shafts that are manufactured from various composite materials or, more particularly, from a set of plies of "pre-preg" composite sheet. Pre-preg composite sheets are formed by pre-impregnating strands of fiber, for example, carbon or glass, within a binding matrix such as a thermoset epoxy resin or thermoplastic resin. The binding matrix or resin is staged such that it holds the fibers together and forms a malleable sheet.
Numerous shafts are now manufactured by wrapping a set of plies of pre-preg composite sheet around a mandrel in a predetermined manner, wrapping the various plies in a binding material such as cellophane or polypropylene tape, and heating the ply-wrapped mandrel to a predetermined temperature for a time sufficient to allow the resin comprising the plies of pre-preg composite sheet to become fully cured. Once the resin has been fully cured, the binding material may be removed from the exterior of the shaft, and the mandrel may be removed from the core of the shaft. Finally, the shaft may be lightly sanded and painted prior to being inserted into a golf club head.
Through the use of composite materials, it has become possible to manufacture reduced weight shafts for golf clubs, and many shaft manufacturers are now offering for sale ultralight shafts having, for example, a mass less than 70 grams. The extent to which the weight of a shaft may be reduced, however, is limited substantially by the structural requirements that must be met by the tip of the shaft that is affixed within the golf club head. In short, if the walls of the shaft tip are made too thin in an effort to reduce the weight of the shaft, the tip will likely fail or shatter during use. This is particularly true for those golf club head designs that employ a shortened hosel, as such designs provide less structural support for the shaft tip.
It will also be noted that, when a golf club head incorporates a bored-through design whereby the shaft extends through the club head, it is generally necessary to affix a plug in the open end of the shaft tip after the shaft tip has been inserted through the golf club head. This gives the assembled golf club a pleasing cosmetic appearance and, more importantly, prevents debris from entering the shaft tip. However, the use of conventional plugs provides little, if any, structural support to the shaft tip.
Finally, it will be noted that many conventional shaft tips are damaged during trimming processes. Once a shaft is formed, it is common to trim the shaft by removing a segment from both the butt end of the shaft and the tip end. If the walls of the tip are too thin, or if proper care is not taken during the trimming process, serious damage may be caused to the tip during the trimming process.
In view of the many problems that may be encountered in designing and manufacturing reduced weight shafts for golf clubs, it is submitted that those skilled in the art would find improved golf club shafts with reinforced tips and methods of manufacturing such shafts to be quite useful.